rcs_kwexp_buf
b2 = rcs_kwexp_buf(b2, pb->file, pb->frev);
bp = rcs_kwexp_buf(bp, file, rev);
if ((bp = rcs_kwexp_buf(bp, rfp, frev)) == NULL) {
BUF *rcs_kwexp_buf(BUF *, RCSFILE *, RCSNUM *);
b1 = rcs_kwexp_buf(b1, file, rev);
b1 = rcs_kwexp_buf(b1, file, rev1);
b2 = rcs_kwexp_buf(b2, file, rev2);